The present invention relates to a circuit arrangement for measuring the resistance of a resistance sensor, for instance a wetness sensor, which is connected to an evaluation circuit.
By way of two example, sensor resistors in the form of strip-shaped electrodes which are interlaced in one another are used for measuring the wetness of the windshield of a motor vehicle. If drops of water contact the two electrodes, then the resistance decreases. The decrease in resistance can be used for automatically controlling a windshield wiper. For a measurement of the resistance, it is necessary fundamentally to apply a voltage to the resistance sensor. However, dc portions of the voltage to be applied can produce electrolysis phenomena between the electrodes, which phenomena leads finally to a limiting of the life of the resistance sensors. A device for controlling a drive means for a vehicle accessory having such a sensor is described, for instance, in WO 90/08680.